This invention relates to improvements in apparatus for transferring objects and more particularly, it concerns an improved transfer mechanism for use principally in the transfer of non-ambulatory patients from a hospital bed or other surface on which they are initially reclined to the mechanism by which they may be supported and/or subsequently transferred to a second surface such as a surgical table, X-ray table or another bed.
The development of patient transferring apparatus of the type to which the present invention pertains is reflected in the disclosures of the following U.S. Pats.: No. 3,493,979 issued Feb. 10, 1970 to Laurel A. Koll and Walter Crook, Jr.; No. 3,579,672 issued May 25, 1971 to Laurel A. Koll and Walter Crook, Jr.; and No. 3,765,037 issued Oct. 16, 1973 to Albert Dunkin. The apparatus disclosed particularly in the latter two of these patents has been commercialized and is currently used in many hospitals and similar institutions.
Such apparatus generally includes a vertically adjustable and wheeled base supporting a transfer mechanism having a fixed deck carrying a pair of laterally translatable superposed, sheet-like apron supporting separator members about which a pair of upper and lower fabric-like aprons are trained. The aprons are established by very thin endless belts formed of teflon coated nylon fabric and are independently controlled in a manner such that during lateral extension of the separators out over a bed and under a patient to be transferred, the respective flight portions of the upper and lower aprons which contact the patient and the bed remain relatively stationary and thus isolate both the patient and the bed from frictional contact with the laterally moving separator plates. When the patient is fully positioned on the assembly of aprons and separator plates, the condition of the upper apron is changed so that the upper flight portion thereof in physical contact with the patient, will move in the same direction and at the same linear speed as the separator plates during retraction to transfer the patient from the bed or other surface back to the deck of the mechanism. The lower flight portion of the lower apron is fixed to the deck so that it remains stationary with respect to the surface of the bed also during the retraction of the separator and apron assembly. Accordingly, the lower flight portion of the upper apron slides relative to the upper flight portion of the lower apron with which it is in frictional contact. Such sliding motion between the aprons or belts is accommodated by the low friction characteristics of the teflon coating and the generation of unwanted static electricity is avoided by rendering the belts electrically conductive.
The basic transfer mechanism disclosed particularly in U.S. Pat. No. 3,579,672 and U.S. Pat. No. 3,765,037 possesses several unique features which are believed to be the basis for its immediate acceptance in the patient transfer field. Perhaps foremost of these features is the universal flexibility of the apron and separator assembly by which this assembly may conform to the irregular and unpredictable contour of the human anatomy reclined on a yieldable surface such as a bed mattress. This feature, combined with the facility for retaining to 130 mm. or less, the thickness of the plate-like transfer assembly movable under the patient to be transferred, enables a combined "softness" and "thinness" which makes it difficult for a bedridden patient to feel the assembly moving beneath him, not to mention a total absence of discomfort. Secondly, the provision for changing the condition of the upper apron relative to its separator plate not only enables the lateral loaded retraction of the assembly of aprons and plates to effect the transfer of the object or patient back to the deck of apparatus, but does so without in any way lifting the object or patient from the surface on which he is initially reclined and with which a patient identifies emotionally. As a result, the transfer of a hospital patient can be accomplished without subjecting the patient to any measure of fear or other emotional disturbance normally associated with patient handling operations.
Although object transfer apparatus of the type disclosed in the aforementioned U.S. patents has proven to be highly effective in the transfer of non-ambulatory hospital patients, there is need for improvement particularly from the standpoint of reduction of manufacturing costs, weight and size. While a need for reduction in manufacturing costs is essentially self-explained, the weight of prior machines has exceeded that of conventional hospital litters to such an extent that it is difficult for a nurse, for example, to manuever the machine within the space ordinarily available next to a bed in a hospital or nursing home environment. In particular, the strength required to change direction, initiate or stop movement of the machine is a practical deterrent to its use for the most routine of patient transfer operations.
With respect to size, the dimension most difficult to reduce and which also is perhaps most important from the standpoint of manueverability in and out of hospital rooms is the overall width of the machine. In this connection, the design of prior machines requires that the rear edge of the separators be retained on the front edge of the machine deck in the maximum extended position of the separators. Since in their retracted position the separators must overlie the machine deck, the separators can be no wider than the deck and thus cannot be extended for patient loading and unloading through a distance in excess of the width of the machine. The magnitude of this problem becomes apparent upon consideration of the fact that the optimum width of a litter for both patient support and manueverability from room to room in hospitals or like institutions should be on the order of 75 cm. However, because the width of a conventional hospital bed is often in excess of 100 cm., the maximum separator extension is less than desirable from the standpoint of extending the separators to a position where they are fully under the patient initially reclined in the center or on the far side of the hospital bed. As a result, it is often necessary to make use of bed sheets or the like to assist in loading a patient from a hospital bed onto the separator assembly for subsequent transfer back to the chassis deck of the transfer apparatus.